The influence of abnormal hip mechanics on knee injury: a biomechanical perspective

The influence of hip strength on lower-limb, pelvis, and trunk kinematics and coordination patterns during walking and hopping in healthy women

STUDY DESIGN

Cross-sectional laboratory study.

OBJECTIVES

To compare peak lower-limb, pelvis, and trunk kinematics and interjoint and intersegmental coordination in women with strong and weak hip muscle performance.

BACKGROUND

Persons with lower extremity musculoskeletal disorders often demonstrate a combination of weak hip musculature and altered kinematics during weight-bearing dynamic tasks. However, the association between hip strength and kinematics independent of pathology or pain is unclear.

METHODS

Peak hip extensor and abductor torques were measured in 150 healthy young women. Of these, 10 fit the criteria for the strong group and 9 for the weak group, representing those with the strongest and weakest hip musculature, respectively, of the 150 screened individuals. Kinematics of the hip, knee, pelvis, and trunk were measured during the stance phases of walking and rate-controlled hopping. Hip/knee and pelvis/trunk coordination were calculated using the vector coding technique.

RESULTS

There were no group differences in peak hip, knee, or pelvis kinematics. Participants in the weak group demonstrated greater trunk lateral bend toward the stance limb during hopping (P = .002, effect size [d] = 1.88). In the transverse plane, those in the weak group utilized less inphase coordination between the hip and the knee during walking (P = .036, d = 1.45) and more antiphase coordination between the hip and knee during hopping (P = .03, d = 1.47).

CONCLUSION

In the absence of pain or pathology, poor hip muscle performance does not affect peak hip or knee joint kinematics in young women, but is associated with significantly different lower-limb and trunk/pelvis coordination during weight-bearing dynamic tasks. J Orthop Sports Phys Ther 2014;44(7):525-531. Epub 10 May 2014. doi:10.2519/jospt.2014.5028.

A preliminary study on the differences in male and female muscle force distribution patterns during squatting and lunging maneuvers

In the United States, 250,000 people tear their anterior cruciate ligament (ACL) annually with females at higher risk of ACL failure than males. By predicting muscle forces during low impact maneuvers we may be able to estimate possible muscle imbalances that could lead to ACL failure during highly dynamic maneuvers. The purpose of this initial study was to predict muscle forces in males and females similar in size and activity level, during squat and lunge maneuvers. We hypothesized that during basic low impact maneuvers (a) distribution of quadriceps forces are different in males and females and (b) females exhibit quadriceps dominance when compared to males. Two males and three females performed squatting and lunging maneuvers while electromyography (EMG) data, motion capture data, and ground reaction forces were collected. Nine individual muscle forces for muscles that cross the knee were estimated using an EMG-driven model. Results suggest that males activate their rectus femoris muscle more than females, who in turn activate their vastus lateralis muscle at their maximum flexion angle, and more their vastus medialis muscle when ascending from a squat. During the lunge maneuver, males used greater biceps femoris force than females, throughout the lunge, and females exhibited higher semitendinosus force. Quadriceps dominance was evident in both males and females during the prescribed tasks, and there was no statistical difference between genders. Understanding individual muscle force distributions in males and females during low impact maneuvers may provide insights regarding failure mechanisms during highly dynamic maneuvers, when ACL injuries are more prevalent.

A regional interdependence model of musculoskeletal dysfunction: research, mechanisms, and clinical implications

The term 'regional interdependence' or RI has recently been introduced into the vernacular of physical therapy and rehabilitation literature as a clinical model of musculoskeletal assessment and intervention. The underlying premise of this model is that seemingly unrelated impairments in remote anatomical regions of the body may contribute to and be associated with a patient's primary report of symptoms. The clinical implication of this premise is that interventions directed at one region of the body will often have effects at remote and seeming unrelated areas. The formalized concept of RI is relatively new and was originally derived in an inductive manner from a variety of earlier publications and clinical observations. However, recent literature has provided additional support to the concept. The primary purpose of this article will be to further refine the operational definition for the concept of RI, examine supporting literature, discuss possible clinically relevant mechanisms, and conclude with a discussion of the implications of these findings on clinical practice and research.

Position-Specific Hip and Knee Kinematics in NCAA Football Athletes

BACKGROUND

Femoroacetabular impingement is a debilitating hip condition commonly affecting athletes playing American football. The condition is associated with reduced hip range of motion; however, little is known about the range-of-motion demands of football athletes. This knowledge is critical to effective management of this condition.

PURPOSE

To (1) develop a normative database of game-like hip and knee kinematics used by football athletes and (2) analyze kinematic data by playing position. The hypothesis was that kinematics would be similar between running backs and defensive backs and between wide receivers and quarterbacks, and that linemen would perform the activities with the most erect lower limb posture.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Forty National Collegiate Athletic Association (NCAA) football athletes, representing 5 playing positions (quarterback, defensive back, running back, wide receiver, offensive lineman), executed game-like maneuvers while lower body kinematics were recorded via optical motion capture. Passive hip range of motion at 90° of hip flexion was assessed using a goniometer. Passive range of motion, athlete physical dimensions, hip function, and hip and knee rotations were submitted to 1-way analysis of variance to test for differences between playing positions. Correlations between maximal hip and knee kinematics and maximal hip kinematics and passive range of motion were also computed.

RESULTS

Hip and knee kinematics were similar across positions. Significant differences arose with linemen, who used lower maximal knee flexion (mean ± SD, 45.04° ± 7.27°) compared with running backs (61.20° ± 6.07°; P < .001) and wide receivers (54.67° ± 6.97°; P = .048) during the cut. No significant differences were found among positions for hip passive range of motion (overall means: 102° ± 15° [flexion]; 25° ± 9° [internal rotation]; 25° ± 8° [external rotation]). Several maximal hip measures were found to negatively correlate with maximal knee kinematics.

CONCLUSION

A normative database of hip and knee kinematics utilized by football athletes was developed. Position-specific analyses revealed that linemen use smaller joint motions when executing dynamic tasks but do not demonstrate passive range of motion deficits compared with other positions.

CLINICAL RELEVANCE

Knowledge of requisite game-like hip and knee ranges of motion is critical for developing goals for nonoperative or surgical recovery of hip and knee range of motion in the symptomatic athlete. These data help to identify playing positions that require remedial hip-related strength and conditioning protocols. Negative correlations between hip and knee kinematics indicated that constrained hip motion, as seen in linemen, could promote injurious motions at the knee.

Neuromuscular dysfunction that may predict ACL injury risk: a case report

This case report examined the neuromuscular function of a competitive female netball player six days prior to an incident where she sustained an acute anterior cruciate ligament injury during normal sports activity. Electromyography was used to examine activation onsets of four lower limb muscles (rectus femoris, biceps femoris, medial hamstrings and gluteus medius) relative to initial contact (IC) during netball-specific landings of varying complexity. The results of the injured participant were compared to the remaining participants in the study (n=8), and the injured participant's injured limb was compared to the contralateral limb. The injured participant was the only player to record delayed pre-injury muscle onsets after IC for all muscles tested in the injured limb, while her non-injured limb was comparable to the other participants tested. Furthermore, delayed muscle onset after IC occurred more frequently as landing complexity increased. This case report suggests that delayed muscle activity onset after IC during landing may be an important risk factor for ACL injury.

Neuromuscular training and muscle strengthening in patients with patellofemoral pain syndrome: a protocol of randomized controlled trial

BACKGROUND

Patellofemoral pain syndrome (PFPS) is a common musculoskeletal condition, particularly among women. Patients with PFPS usually experience weakness in the gluteal muscles, as well as pain and impaired motor control during activities of daily living. Strengthening the hip muscles is an effective way of treating this disorder. Neuromuscular training has also been identified as a therapeutic tool, although the benefits of this intervention in patients with PFPS patients remain inconclusive.

DESIGN

This is a protocol of randomized controlled trial with a blind assessor. Thirty-four women with a clinical diagnosis of PFPS participated. These participants were allocated into two groups (experimental and control). The experimental group performed twelve sessions to strengthen the knee extensors, hip abductor and lateral rotator muscles in association with neuromuscular training of the trunk and lower extremities. The control group performed the same number of sessions to strengthen the muscles of the hip and knee. The primary outcome was functional capacity (Anterior Knee Pain Scale - AKPS) at 4 weeks. Pain intensity, muscle strength and kinematic changes were also measured during the step down test after four weeks of intervention. Follow up assessments were conducted after three and six months to assess functional capacity and pain. The effects of the treatment (i.e. between-group differences) were calculated using mixed linear models.

DISCUSSION

The present study was initiated on the 1st of April 2013 and is currently in progress. The results of this study may introduce another effective technique of conservative treatment and could guide physical therapists in the clinical decision-making process for women with PFPS.

TRIAL REGISTRATION

Current Controlled Trials NCT01804608.

Propulsion phase of the single leg triple hop test in women with patellofemoral pain syndrome: a biomechanical study

Asymmetry in the alignment of the lower limbs during weight-bearing activities is associated with patellofemoral pain syndrome (PFPS), caused by an increase in patellofemoral (PF) joint stress. High neuromuscular demands are placed on the lower limb during the propulsion phase of the single leg triple hop test (SLTHT), which may influence biomechanical behavior. The aim of the present cross-sectional study was to compare kinematic, kinetic and muscle activity in the trunk and lower limb during propulsion in the SLTHT using women with PFPS and pain free controls. The following measurements were made using 20 women with PFPS and 20 controls during propulsion in the SLTHT: kinematics of the trunk, pelvis, hip, and knee; kinetics of the hip, knee and ankle; and muscle activation of the gluteus maximus (GM), gluteus medius (GMed), biceps femoris (BF) and vastus lateralis (VL). Differences between groups were calculated using three separate sets of multivariate analysis of variance for kinematics, kinetics, and electromyographic data. Women with PFPS exhibited ipsilateral trunk lean; greater trunk flexion; greater contralateral pelvic drop; greater hip adduction and internal rotation; greater ankle pronation; greater internal hip abductor and ankle supinator moments; lower internal hip, knee and ankle extensor moments; and greater GM, GMed, BL, and VL muscle activity. The results of the present study are related to abnormal movement patterns in women with PFPS. We speculated that these findings constitute strategies to control a deficient dynamic alignment of the trunk and lower limb and to avoid PF pain. However, the greater BF and VL activity and the extensor pattern found for the hip, knee, and ankle of women with PFPS may contribute to increased PF stress.

FMS™ scores and low-back loading during lifting--whole-body movement screening as an ergonomic tool?

BACKGROUND

Previous research suggests that a general whole-body movement screen could be used to identify personal movement attributes that promote potentially injurious low-back loading patterns at work. The purpose of this study was to examine the relationship between Functional Movement Screen™ (FMS) composite scores and the low-back loading response to lifting.

METHODS

Fifteen men who scored greater than 14 on the FMS (high-scorers) and 15 height- and weight-matched low-scorers (FMS < 14) performed sagittally symmetric and asymmetric laboratory-based lifting tasks. A three-dimensional dynamic biomechanical model was used to calculate peak low-back loading levels, and the angle of the lumbar spine was captured at the instant when the peak compressive force was applied.

RESULTS

Regardless of the lifting task performed, there were no differences in peak low-back compression (p ≥ 0.4157), anterior/posterior reaction shear (p ≥ 0.5645), or medial/lateral reaction shear (p ≥ 0.2581) forces between the high- and low-scorers. At the instant when peak compressive forces were applied, differences in the lumbar spine angle between high- and low-scores were not statistically significant about the lateral bend (p ≥ 0.4215), axial twist (p ≥ 0.2734), or flexion/extension (p ≥ 0.1354) axes, but there was a tendency for the lumbar spine to be more deviated in the low-scorers.

CONCLUSIONS

Using the previously established injury prediction threshold value of 14, the composite FMS score was not related to the peak low-back loading magnitudes in lifting. Though not statistically significant, the tendency for the lumbar spines of low-scorers to be more deviated when the peak low-back compression force was imposed could be biomechanically meaningful because spinal load tolerance varies with posture. Future attempts to modify or reinterpret FMS scoring are warranted given that several previous studies have revealed links between composite FMS scores and musculoskeletal complaints.

Comparison of landing biomechanics between male and female dancers and athletes, part 1: Influence of sex on risk of anterior cruciate ligament injury

BACKGROUND

The incidence of anterior cruciate ligament (ACL) injuries among dancers is much lower than among team sport athletes, and no clear disparity between sexes has been reported in the dance population. Although numerous studies have observed differences in landing biomechanics of the lower extremity between male and female team sport athletes, there is currently little research examining the landing biomechanics of male and female dancers and none comparing athletes to dancers. Comparing the landing biomechanics within these populations may help explain the lower overall ACL injury rates and lack of sex disparity.

HYPOTHESIS

The purpose was to compare the effects of sex and group (dancer vs team sport athlete) on single-legged drop-landing biomechanics. The primary hypothesis was that female dancers would perform a drop-landing task without demonstrating typical sex-related risk factors associated with ACL injuries. A secondary hypothesis was that female team sport athletes would display typical ACL risk factors during the same task.

STUDY DESIGN

Controlled laboratory study.

METHODS

Kinematics and kinetics were recorded as 40 elite modern and ballet dancers (20 men and 20 women) and 40 team sport athletes (20 men and 20 women) performed single-legged drop landings from a 30-cm platform. Joint kinematics and kinetics were compared between groups and sexes with a group-by-sex multivariate analysis of variance (MANOVA) followed by pairwise t tests.

RESULTS

Dancers of both sexes and male team sport athletes landed similarly in terms of frontal-plane knee alignment, whereas female team sport athletes landed with a significantly greater peak knee valgus (P = .007). Female dancers were found to have a lower hip adduction torque than those of the other 3 groups (P = .003). Dancers (male and female) exhibited a lower trunk side flexion (P = .002) and lower trunk forward flexion (P = .032) compared with team sport athletes.

CONCLUSION

In executing a 30-cm drop landing, female team sport athletes displayed a greater knee valgus than did the other 3 groups. Dancers exhibited better trunk stability than did athletes.

CLINICAL RELEVANCE

These biomechanical findings may provide insight into the cause of the epidemiological differences in ACL injuries between dancers and athletes and the lack of a sex disparity within dancers.

Trunk and lower extremity segment kinematics and their relationship to pain following movement instruction during a single-leg squat in females with dynamic knee valgus and patellofemoral pain

OBJECTIVES

To understand how instructing females with patellofemoral pain to correct dynamic knee valgus affects pelvis, femur, tibia and trunk segment kinematics. To determine if pain reduction in the corrected condition was associated with improved segment kinematics.

DESIGN

Cross-sectional.

METHODS

A 3D-motion capture system was used to collect multi-joint kinematics on 20 females with dynamic knee valgus and patellofemoral pain during a single-leg squat in two conditions: usual movement pattern, and corrected dynamic knee valgus. During each condition pain was assessed using a visual analog scale. Pelvis, femur, tibia and trunk kinematics in the frontal and transverse planes were compared between conditions using a paired T-test. Pearson correlation coefficients were generated between visual analog scale score and the kinematic variables in the corrected condition.

RESULTS

In the corrected condition subjects had increased lateral flexion of the pelvis toward the weight-bearing limb (p<0.001), decreased femoral adduction (p=0.001) and internal rotation (p=0.01). A trend toward decreased tibial internal rotation (p=0.057) and increased trunk lateral flexion toward the weight-bearing limb (p=0.055) was also found. Lower pain levels were associated with less femoral internal rotation (p=0.04) and greater trunk lateral flexion toward the weight-bearing limb (p=0.055).

CONCLUSIONS

Decreased hip adduction after instruction was comprised of motion at both the pelvis and femur. Decreased pain levels were associated with lower extremity segment kinematics moving in the direction opposite to dynamic knee valgus. These results increase our understanding of correction strategies used by females with patellofemoral pain and provide insight for rehabilitation.

Isometric strength ratios of the hip musculature in females with patellofemoral pain: a comparison to pain-free controls

The purpose of the study was to compare hip agonist-antagonist isometric strength ratios between females with patellofemoral pain (PFP) syndrome and pain-free control group. One hundred and twenty females between 15 and 40 years of age (control group: n = 60; PFP group: n = 60) participated in the study. Hip adductor, abductor, medial rotator, lateral rotator, flexor, and extensor isometric strength were measured using a hand-held dynamometer. Comparisons in the hip adductor/abductor and medial/lateral rotator and flexor/extensor strength ratios were made between groups using independent t-tests. Group comparisons also were made between the anteromedial hip complex (adductor, medial rotator, and flexor musculature) and posterolateral hip complex (abductor, lateral rotator, and extensor musculature). On average, the hip adductor/abductor isometric strength ratio in the PFP group was 23% higher when compared with the control group (p = 0.01). The anteromedial/posterolateral complex ratio also was significantly higher in the PFP group (average 8%; p = 0.04). No significant group differences were found for the medial/lateral rotator ratio and flexor/extensor strength ratios. The results of this study demonstrate that females with PFP have altered hip strength ratios when compared with asymptomatic controls. These strength imbalances may explain the tendency of females with PFP to demonstrate kinematic tendencies that increase loading on the patellofemoral joint (i.e., dynamic knee valgus).

Effects of functional stabilization training on pain, function, and lower extremity biomechanics in women with patellofemoral pain: a randomized clinical trial

STUDY DESIGN

Randomized clinical trial.

OBJECTIVES

To compare the effects of functional stabilization training (FST) versus standard training on knee pain and function, lower-limb and trunk kinematics, trunk muscle endurance, and eccentric hip and knee muscle strength in women with patellofemoral pain.

BACKGROUND

A combination of hip- and knee-strengthening exercise may be more beneficial than quadriceps strengthening alone to improve pain and function in individuals with patellofemoral pain. However, there is limited evidence of the effectiveness of these exercise programs on the biomechanics of the lower extremity.

METHODS

Thirty-one women were randomized to either the FST group or standard-training group. Patients attended a baseline assessment session, followed by an 8-week intervention, and were reassessed at the end of the intervention and at 3 months after the intervention. Assessment measures were a 10-cm visual analog scale for pain, the Lower Extremity Functional Scale, and the single-leg triple-hop test. A global rating of change scale was used to measure perceived improvement. Kinematics were assessed during the single-leg squat. Outcome measures also included trunk endurance and eccentric hip and knee muscle strength assessment.

RESULTS

The patients in the FST group had less pain at the 3-month follow-up and greater global improvement and physical function at the end of the intervention compared to those in the standard-training group. Lesser ipsilateral trunk inclination, pelvis contralateral depression, hip adduction, and knee abduction, along with greater pelvis anteversion and hip flexion movement excursions during the single-leg squat, were only observed in the FST group after the intervention. Only those in the FST group had greater eccentric hip abductor and knee flexor strength, as well as greater endurance of the anterior, posterior, and lateral trunk muscles, after training.

CONCLUSION

An intervention program consisting of hip muscle strengthening and lower-limb and trunk movement control exercises was more beneficial in improving pain, physical function, kinematics, and muscle strength compared to a program of quadriceps-strengthening exercises alone.

Musculoskeletal predictors of movement quality for the forward step-down test in asymptomatic women

STUDY DESIGN

Cross-sectional.

OBJECTIVE

To investigate the interrater reliability of movement-quality ratings for the forward step-down (FSD) test and to compare hip muscle strength and lower extremity joint range of motion and muscle flexibility among asymptomatic women with different levels of movement quality.

BACKGROUND

The interrater reliability of the FSD test has not yet been investigated. Additionally, it is not known whether differences in musculoskeletal measures exist among individuals with different levels of movement quality during the FSD test.

METHODS

Two physical therapists assessed movement quality during the FSD test in 26 asymptomatic women (mean ± SD age, 22.7 ± 0.9 years). Hip muscle strength and lower extremity joint range of motion and muscle flexibility were also assessed. The interrater reliability of the FSD test was estimated by using the kappa coefficient and percent agreement. Differences in musculoskeletal measures based on movement quality were assessed by independent t tests.

RESULTS

The kappa coefficient and percent agreement for rating the quality of movement on the FSD test were 0.80 (95% confidence interval: 0.57, 1.00) and 85%, respectively. The subjects with moderate movement quality had significantly less strength of the hip abductors, less knee flexion range of motion measured in prone (quadriceps flexibility), and less hip adduction range of motion measured in sidelying (iliotibial band/tensor fascia latae flexibility) compared to those with good movement quality.

CONCLUSION

There was good agreement for the rating of movement quality during the FSD test, and there were physical attributes that distinguished those with moderate from those with good quality of movement.

Improvements in hip muscle performance result in increased use of the hip extensors and abductors during a landing task

BACKGROUND

Impaired hip muscle performance has been implicated as a contributing factor to the increased risk of anterior cruciate ligament (ACL) injury in women.

PURPOSE

To determine the influence of a hip-focused training program on lower extremity biomechanics during a drop-jump task.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twenty-one recreationally active women (18-25 years of age) participated in a 4-week training program consisting of hip-focused plyometric and balance perturbation exercises (3 times/wk, 30 min/session). Maximum isometric strength of the hip extensors, hip abductors, and knee extensors was assessed, along with lower extremity biomechanics during a drop-jump task. All assessments were performed within 5 days of initiation and completion of the training program.

RESULTS

After training, subjects demonstrated significantly greater maximum isometric strength of the hip extensors (2.87 ± 0.7 vs 3.11 ± 0.7 N·m/kg; P < .01) and hip abductors (2.08 ± 0.7 vs 2.23 ± 0.07 N·m/kg; P = .004). No significant difference in knee extensor strength was observed. After training, subjects landed with significantly greater peak knee flexion (94.0° ± 8.5° vs 98.0° ± 10.1°; P < .001) and hip flexion (83.4° ± 7.6° vs 89.9° ± 8.8°; P = .008) and a lower knee/hip extensor moment ratio (1.33 ± 0.6 vs 0.99 ± 0.3; P = .001). In addition, subjects demonstrated significantly lower peak knee abduction angles (6.8° ± 3.3° vs 5.6° ± 3.1°; P = .04) and average knee adductor moments (0.06 ± 0.1 vs -0.02 ± 0.1 N·m/kg; P < .001).

CONCLUSION

Changes in lower extremity biomechanics consistent with decreased risk for ACL injury were observed after participation in a hip-focused training program.

CLINICAL RELEVANCE

The study results suggest that ACL injury prevention programs targeting hip muscle performance may be important in mitigating biomechanical risk factors associated with ACL injury in women.

Rehabilitation of proximal hamstring tendinopathy utilizing eccentric training, lumbopelvic stabilization, and trigger point dry needling: 2 case reports

STUDY DESIGN

Case report.

BACKGROUND

Proximal hamstring tendinopathy is a relatively uncommon overuse injury seen in runners. In contrast to the significant amount of literature guiding the evaluation and treatment of hamstring strains, there is little literature about the physical therapy management of proximal hamstring tendinopathy, other than the general recommendations to increase strength and flexibility.

CASE DESCRIPTION

Two runners were treated in physical therapy for proximal hamstring tendinopathy. Each presented with buttock pain with running and sitting, as well as tenderness to palpation at the ischial tuberosity. Each patient was prescribed a specific exercise program focusing on eccentric loading of the hamstrings and lumbopelvic stabilization exercises. Trigger point dry needling was also used with both runners to facilitate improved joint motion and to decrease pain.

OUTCOMES

Both patients were treated in 8 to 9 visits over 8 to 10 weeks. Clinically significant improvements were seen in pain, tenderness, and function in each case. Each patient returned to running and sitting without symptoms.

DISCUSSION

Proximal hamstring tendinopathy can be difficult to treat. In these 2 runners, eccentric loading of the hamstrings, lumbopelvic stabilization exercises, and trigger point dry needling provided short- and long-term pain reduction and functional benefits. Further research is needed to determine the effectiveness of this cluster of interventions for this condition.

LEVEL OF EVIDENCE

Therapy, level 4.

Frontal Plane Running Biomechanics in Female Runners With Previous Iliotibial Band Syndrome

Proximal factors such as excessive frontal plane pelvis and trunk motion have been postulated to be biomechanical risk factors associated with iliotibial band syndrome. In addition, lateral core endurance deficiencies may be related to increased pelvis and trunk motion during running. The purpose of this cross-sectional investigation was to determine if differences in biomechanics during running, as well as lateral core endurance exist between female runners with previous iliotibial band syndrome and controls. Gait and lateral core endurance were assessed in 34 female runners (17 with previous iliotibial band syndrome). Multivariate analysis of variance was performed to assess between group difference in pelvis, trunk, hip, and knee variables of interest. Runners with previous iliotibial band syndrome exhibited similar peak trunk lateral flexion, peak contralateral pelvic drop, peak hip adduction, and peak external knee adduction moment compared with controls. In addition, trunk-pelvis coordination was similar between groups. Contrary to our hypotheses, both groups exhibited trunk ipsilateral flexion. Lateral core endurance was not different between groups. These findings provide the first frontal plane pelvis and trunk kinematic data set in female runners with previous iliotibial band syndrome. Frontal plane pelvis and trunk motion may not be associated with iliotibial band syndrome.

Posterolateral hip muscle strengthening versus quadriceps strengthening for patellofemoral pain: a comparative control trial

OBJECTIVE

To compare the efficacy of posterolateral hip muscle strengthening versus quadriceps strengthening in reducing pain and improving health status in persons with patellofemoral pain (PFP).

DESIGN

Comparative control trial.

SETTING

Rehabilitation facility.

PARTICIPANTS

Persons with a diagnosis of PFP (N=36; 18 men, 18 women).

INTERVENTIONS

Patients were alternately assigned to a posterolateral hip muscle strengthening group (9 men and 9 women) or a quadriceps strengthening group (9 men and 9 women). The posterolateral hip muscle strengthening group performed hip abductor and external rotator strengthening exercises, whereas the quadriceps strengthening group performed quadriceps strengthening exercises (3 times a week for 8wk).

MAIN OUTCOME MEASURES

Pain (visual analog scale [VAS]) and health status (Western Ontario McMaster Universities Osteoarthritis Index [WOMAC]) were assessed at baseline, postintervention, and 6-month follow-up.

RESULTS

Significant improvements in VAS and WOMAC scores were observed in both groups from baseline to postintervention and baseline to 6-month follow-up (P<.001). Improvements in VAS and WOMAC scores in the posterolateral hip exercise group were superior to those in the quadriceps exercise group postintervention and at 6-month follow-up (P<.05).

CONCLUSIONS

Although both intervention programs resulted in decreased pain and improved function in persons with PFP, outcomes in the posterolateral hip exercise group were superior to the quadriceps exercise group. The superior outcomes obtained in the posterolateral hip exercise group were maintained 6 months postintervention.

Chronic Low Back Pain in Women: Muscle Activation during Task Performance

[Purpose] The aim of this study was to compare the activities of the trunk and hip muscles in chronic low back pain (CLBP) women and asymptomatic subjects during the kneeling to half-kneeling task. [Subjects] Twenty-nine CLBP women and thirty asymptomatic subjects (C) participated in this study. [Methods] Electromyography activity (EMG) of the obliquus internus abdominis (OI), the lumbar erector spinae (LES) and the gluteus medius (GM) muscles was recorded bilaterally. The peak amplitude, the time of peak amplitude and the integrated linear envelope EMG for each muscle were obtained. [Results] The C group bilateral OI and GM muscles displayed higher peak amplitudes and earlier times of peak amplitude. They also had higher integrated linear envelope EMG values. The CLBP group bilateral LES muscles had higher peak amplitudes and earlier times of peak amplitude. They also showed an increased integrated linear envelope EMG values. [Conclusion] The CLBP women activate the LES muscles in the kneeling to half-kneeling task, showing different patterns of motor planning activity.

Effect of plyometric training on lower limb biomechanics in females

OBJECTIVE

To verify the effects of plyometric training on lower limb kinematics, eccentric hip and knee torques, and functional performance.

DESIGN

Cohort study.

SETTING

Research laboratory.

PARTICIPANTS

Thirty-six females were divided into a training group (TG; n = 18) that carried out the plyometric training for 8 weeks, and a control group (CG; n = 18) that carried out no physical training.

INTERVENTIONS

Twenty-four plyometric training sessions during approximately 8 weeks with 3 sessions per week on alternate days.

MAIN OUTCOMES MEASURES

Lower limb kinematics (maximum excursion of hip adduction, hip medial rotation, and knee abduction during the single leg squat), eccentric hip (abductor, adductor, medial, and lateral rotator) isokinetic peak torques and knee (flexor and extensor) isokinetic peak torques, and functional performance (triple hop test and the 6-m timed hop test).

RESULTS

After 8 weeks, only the TG significantly reduced the values for the maximum excursion of knee abduction (P = 0.01) and hip adduction (P < 0.001). Similarly, only the TG significantly increased the eccentric hip abductor (P < 0.001) and adductor (P = 0.01) torques. Finally, only the TG significantly increased the values in the triple hop test (P < 0.001) and significantly decreased the values in the 6-m timed hop test (P < 0.001) after intervention.

CONCLUSION

Plyometric training alters lower limb kinematics and increases eccentric hip torque and functional performance, suggesting the incorporation of these exercises in preventive programs for ACL injuries.

Test-retest reliability of three-dimensional kinematics using an electromagnetic tracking system during single-leg squat and stepping maneuver

The electromagnetic tracking system (ETS) has been used to analyze three-dimensional (3D) lower limb kinematics. The single-leg squat and stepping maneuver are useful tasks to evaluate lower extremity alignment in a clinical setting. The purpose of this study was to evaluate the test-retest reliability of trunk, pelvis, hip, and knee 3D kinematics using an ETS during single-leg squat and stepping maneuver and compare 3D kinematics between tasks. Twenty healthy volunteers (10 males and 10 females) completed two test sessions 3-5 days apart. Three-dimensional kinematics using an ETS was assessed during single-leg squat and stepping maneuver. Overall, intrarater-intrasession reliability (ICCs=0.83-1.00) and intersession reliabilities (ICCs=0.82-0.97) were high during single-leg squat and stepping maneuver. The intrasession minimal detectable change (MDC) ranged from 1.3° for the knee frontal plane range of motion for single-leg squat to 6.2° for the pelvic transverse range of motion for the stepping maneuver. Intersession MDC values ranged from 1.2° for the ipsilateral trunk lean for the single-leg squat to 8.3° for hip flexion for the stepping maneuver. Healthy participants exhibited greater anterior pelvic tilt, more hip flexion, and less contralateral pelvis forward excursion (p<0.05) during single-leg squat compared with the stepping maneuver. These findings suggest that the 3D kinematics of the trunk, pelvis, hip, and knee using an ETS is reliable during single-leg squat and the stepping maneuver. Minimal detectable change values were low during the evaluated activities. Intertask comparisons revealed differences in hip and pelvis kinematics.

Varied response to mirror gait retraining of gluteus medius control, hip kinematics, pain, and function in 2 female runners with patellofemoral pain

STUDY DESIGN

Case report.

BACKGROUND

The underlying mechanism of the changes in running mechanics after gait retraining is presently unknown. This case report assesses changes in muscle coordination and kinematics during treadmill running and step ascent in 2 female runners with patellofemoral pain after mirror gait retraining.

CASE DESCRIPTION

Two female runners with chronic patellofemoral pain underwent 8 sessions of mirror gait retraining during treadmill running. Subjective measures and hip abductor strength were recorded at baseline and after the retraining phase. Changes in hip mechanics and electromyography data of the gluteus medius during treadmill running and step ascent were also assessed.

OUTCOMES

Both runners reported improvements in pain and function that were maintained for at least 3 months. During running, peak contralateral pelvic drop (baseline-postretraining difference: runner 1, 2.6° less; runner 2, 1.7° less) and peak hip adduction (baseline-postretraining difference: runner 1, 5.2° less; runner 2, 6.3° less) were reduced after retraining. Kinematic reductions accompanied earlier activation of the gluteus medius relative to foot strike (baseline-postretraining difference: runner 1, 12.6 milliseconds earlier; runner 2, 37.3 milliseconds earlier) and longer duration of gluteus medius activity (runner 1, 55.8 milliseconds longer; runner 2, 44.4 milliseconds longer). Runner 1 transferred reduced contralateral pelvic drop to step ascent, whereas runner 2 did not (contralateral pelvic drop baseline-postretraining difference: runner 1, 3.6° less; runner 2, 1.5° more; hip adduction baseline-postretraining difference: runner 1, 3.0° less; runner 2, 0.5° more). Both runners demonstrated earlier onset of gluteus medius activity during step ascent (baseline-postretraining difference: runner 1, 48.0 milliseconds earlier; runner 2, 28.3 milliseconds earlier), but only runner 1 demonstrated longer activation duration (runner 1, 25.0 milliseconds longer; runner 2, 69.4 milliseconds shorter).

DISCUSSION

While changes in hip mechanics and gluteus medius activity during running were consistent with those noted during step ascent for runner 1, runner 2 failed to demonstrate similar consistency between the tasks. Earlier onset and longer duration of gluteus medius activity may have been necessary to alter step mechanics for runner 2.

LEVEL OF EVIDENCE

Therapy, level 4.

Effects of the use of oral contraceptives on hip and knee kinematics in healthy women during anterior stair descent

PURPOSE

Our aim was to evaluate the effects of the use of oral contraceptives (OC) on the hip and knee kinematics of healthy women during anterior stair descent.

METHODS

Forty volunteers aged from 18 to 26 years were divided into two groups: 1-Group of women who had used OC for at least 3 months prior to evaluation (n = 20) and 2-Group of women who did not use OC (n = 20). The knee flexion/extension and abduction/adduction, hip flexion/extension, abduction/adduction and medial/lateral rotation excursions (degrees) were calculated for the dominant (supporting) limb during anterior stair descent. T tests for independent samples were used to compare the kinematic differences between the groups (α = 0.05).

RESULTS

No significant difference was verified between the groups regarding the maximum excursion of knee flexion (n.s.) and abduction (n.s.) or hip flexion (n.s.), adduction (n.s.) and medial rotation (n.s.). When considering the knee flexion at 50°, no significant difference was verified between the groups regarding the excursion of knee abduction (n.s.) or hip flexion (n.s.) adduction (n.s.) and medial/lateral rotation (n.s.).

CONCLUSION

These results suggest that the use of OC does not influence the hip and knee kinematics during anterior stair descent. Therefore, the role of this medication as a protective factor against anterior cruciate ligament injuries remains questionable.

Influence of the hip flexion angle on isokinetic hip rotator torque and acceleration time of the hip rotator muscles

The purpose of this study was to verify the influence of the hip flexion angle on isokinetic rotator torque and acceleration times of the hip medial and lateral rotator muscles. Twenty-one healthy women were included in this study. The hip rotator function was evaluated at 3 different hip flexion angles (10°, 40°, and 90°). The results showed that both eccentric and concentric hip lateral rotator torques were greater at 40° of hip flexion when compared with 90°. Moreover, both the eccentric and concentric hip medial rotator torques were greater at 90° of hip flexion than at 40° and 10°, and greater at 40° than at 10°. In addition, both the eccentric and concentric hip medial to lateral rotator torque ratios were greater at 90° of hip flexion than at 40° and 10°, and greater at 40° than at 10°. Finally, the acceleration times of the hip medial rotator muscles were smaller at 90° of hip flexion than at 10° and smaller at 40° than at 10°. The current results highlight the importance of evaluating the hip rotator muscles at different hip flexion angles to comprehensively assess their functions.

Trunk and hip biomechanics influence anterior cruciate loading mechanisms in physically active participants

BACKGROUND

Excessive trunk motion and deficits in neuromuscular control (NMC) of the lumbopelvic hip complex are risk factors for anterior cruciate ligament (ACL) injury. However, the relationship between trunk motion, NMC of the lumbopelvic hip complex, and triplanar knee loads during a sidestep cutting task has not been examined.

PURPOSE

To determine if there is an association between multiplanar trunk motion, NMC of the lumbopelvic hip complex, and triplanar knee loads with ACL injury during a sidestep cutting task.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The hip and knee biomechanics and trunk motion of 30 participants (15 male, 15 female) were analyzed during a sidestep cutting task using an optoelectric camera system interfaced to a force plate. Trunk and lower extremity biomechanics were calculated from the kinematic and ground-reaction force data during the first 50% of the stance time during the cutting task. Pearson product moment correlation coefficients were calculated between trunk and lower extremity biomechanics. Multiple linear regression analyses were carried out to determine the amount of variance in triplanar knee loading explained by trunk motion and hip moments.

RESULTS

A greater internal knee varus moment (mean, 0.11 ± 0.12 N·m/kg*m) was associated with less transverse-plane trunk rotation away from the stance limb (mean, 20.25° ± 4.42°; r = -0.46, P = .011) and a greater internal hip adduction moment (mean, 0.33 ± 0.25 N·m/kg*m; r = 0.83, P < .05). A greater internal knee external rotation moment (mean, 0.11 ± 0.08 N·m/kg*m) was associated with a greater forward trunk flexion (mean, 7.62° ± 5.28°; r = 0.42, P = .020) and a greater hip internal rotation moment (mean, 0.15 ± 0.16 N·m/kg*m; r = 0.59, P = .001). Trunk rotation and hip adduction moment explained 81% (P < .05) of the variance in knee varus moment. Trunk flexion and hip internal rotation moment explained 48% (P < .05) of the variance in knee external rotation moment.

CONCLUSION

Limited trunk rotation displacement toward the new direction of travel and hip adduction moment are associated with an increased internal knee varus moment, while a combined increase in trunk flexion displacement and hip internal rotation moment is associated with a higher internal knee external rotation moment.

CLINICAL RELEVANCE

Prevention interventions for ACL injury should encourage trunk rotation toward the new direction of travel and limit excessive trunk flexion while adjusting frontal- and transverse-plane hip NMC.

Does quadriceps atrophy exist in individuals with patellofemoral pain? A systematic literature review with meta-analysis

STUDY DESIGN

Systematic literature review.

OBJECTIVES

To investigate whether quadriceps atrophy is present in the affected limb of individuals with patellofemoral pain (PFP).

BACKGROUND

PFP is a common condition. Atrophy of the quadriceps femoris, in particular the vastus medialis obliquus, is often assumed to be present by clinicians, and its resolution may underpin the reported effectiveness of quadriceps strengthening intervention in PFP rehabilitation.

METHODS

A systematic search of the literature was conducted to identify studies that measured the size of the quadriceps in individuals with PFP. Meta-analyses were performed to determine whether quadriceps size in limbs with PFP differed from that in comparison limbs. Separate meta-analyses were performed for quadriceps size measured as girth and quadriceps size measured with imaging (thickness, cross-sectional area, and volume).

RESULTS

Ten studies were included in this review. The meta-analysis of girth measurements (3 studies) found no atrophy in limbs with PFP (P = .638). The meta-analyses for imaging techniques (thickness, cross-sectional area, or volume measurements) showed atrophy in the limb with PFP compared to both the asymptomatic limb (3 studies) (P = .036) and limbs from a comparison group (3 studies) (P = .001). The single study that compared the vastus medialis obliquus and vastus lateralis in individuals with PFP found atrophy of both the vastus medialis obliquus and vastus lateralis but no significant difference in the amount of atrophy between them (P = .179).

CONCLUSION

Quadriceps muscle atrophy was shown to be present in PFP when analyzed by imaging, but not by girth measures. Insufficient data were available to determine if there was greater atrophy of the vastus medialis obliquus than the vastus lateralis. These findings support the rationale for use of quadriceps strengthening as part of a rehabilitation program for PFP.

Do knee concentric and eccentric strength and sagittal-plane knee joint biomechanics differ between jumpers and non-jumpers in landing?

The purpose of this study was to investigate the differences of knee concentric and eccentric strength and impact related knee biomechanics between jumpers and non-jumpers during step-off landing tasks. Ten male college swimming athletes (non-jumpers) and 10 track and volleyball athletes (jumpers) were recruited to participate in two test sessions: a muscle strength testing session of concentric and eccentric extension for dominant knee joint at 60°/s and 180°/s and a landing testing session. The participants performed five trials of step-off landing in each of four conditions: soft and stiff landing from 0.4m and 0.6m landing heights. The three-dimensional kinematics and ground reaction force were recorded simultaneously during step-off landing conditions. The results showed that the jumpers had significantly greater peak knee eccentric extension and concentric flexion torques compared to the non-jumpers. No significant group effects were found for peak vertical ground reaction force and knee range of motion during landing. The jumpers had significantly greater knee contact flexion angle, maximum knee flexion angle and initial knee extension moment compared to the non-jumpers. These results suggest that these athletes adopted a favorable impact attenuation strategy that is related to the greater knee eccentric muscle strength and training.

A biomechanical perspective on physical therapy management of knee osteoarthritis

SYNOPSIS

Altered knee joint biomechanics and excessive joint loading have long been considered as important contributors to the development and progression of knee osteoarthritis. Therefore, a better understanding of how various treatment options influence the loading environment of the knee joint could have practical implications for devising more effective physical therapy management strategies. The aim of this clinical commentary was to review the pertinent biomechanical evidence supporting the use of treatment options intended to provide protection against excessive joint loading while offering symptomatic relief and functional improvements for better long-term management of patients with knee osteoarthritis. The biomechanical and clinical evidence regarding the effectiveness of knee joint offloading strategies, including contralateral cane use, laterally wedged shoe insoles, variable-stiffness shoes, valgus knee bracing, and gait-modification strategies, within the context of effective disease management is discussed. In addition, the potential role of therapeutic exercise and neuromuscular training to improve the mechanical environment of the knee joint is considered. Management strategies for treatment of joint instability and patellofemoral compartment disease are also mentioned. Based on the evidence presented as part of this clinical commentary, it is argued that special considerations for the role of knee joint biomechanics and excessive joint loading are necessary in designing effective short- and long-term management strategies for treatment of patients with knee osteoarthritis.

LEVEL OF EVIDENCE

Therapy, level 5.

Lumbopelvic manipulation in patients with patellofemoral pain syndrome

OBJECTIVES

A recent clinical prediction rule (CPR) identified characteristics that may predict an immediate reduction in pain following lumbopelvic manipulation in patients with patellofemoral pain syndrome. The purpose of this single-arm cohort study was to replicate the proposed CPR in a different population and investigate changes in self-reported pain, hip range of motion, strength, and function immediately following lumbopelvic manipulation.

METHODS

Forty-four subjects (63·6% female; mean age 27·4 years) met inclusion criteria. Hip internal rotation range of motion, lower extremity strength using a handheld dynamometer, and single/triple hop tests were assessed prior to and immediately following a spinal manipulation. A global rating of change questionnaire was administered after testing and telephonically at 1 week. Paired t-tests compared pre- and post-manipulation range of motion, strength, and hop test limb symmetry indices (α = 0·05).

RESULTS

Fifty-seven percent of subjects had a successful outcome measured by the numerical pain rating scale immediately following manipulation. Twenty-five of subjects experienced a successful outcome as measured by the global rating of change questionnaire at 1 week. No single individual or combination of predictor variables predicted a positive outcome immediately following the lumbopelvic manipulation (+likelihood ratio 0·7 with three of five predictor variables present). Statistically significant differences (P<0·05) were found in hip extension and abduction strength and hip internal rotation symmetry post-manipulation, but do not appear to be clinically meaningful.

DISCUSSION

The previously identified CPR was not able to be replicated and no clinically meaningful changes in range of motion, strength, or function were apparent. Future research should focus on a comprehensive impairment-based treatment approach in patients with patellofemoral pain syndrome.

Gender Differences in Lower Limb Kinematics During Stair Descent

The purpose of this study was to compare lower limb kinematics between genders during stair descent. Fifteen females and fifteen males who were healthy and active were included in this study. The lower limb kinematics (pelvis, femur and knee) in the coronal and transversal planes were assessed during stair descent at 30°, 40°, 50° and 60° of knee flexion. The study found that females showed greater knee medial rotation for all the knee flexion angles (P= .02−.001), greater femoral adduction (P= .01 for all variables), with exception for 30° (P= .13), and greater femoral lateral rotation at 60° (P= .04). Females also showed a trend to have greater knee valgus at all the knee flexion angles (P= .06−.11) as well as less contralateral pelvis elevation at 50° and 60° (P= .10 and .12, respectively). This study showed that females carry out the stair descent with a lower limb alignment that might predispose them to develop overuse knee injuries, such as the iliotibial band syndrome and patellofemoral pain syndrome. Further prospective investigations should be carried out to verify whether these variables are factors that could predict these knee injuries.

Frontal plane knee and hip kinematics during sit-to-stand and proximal lower extremity strength in persons with patellofemoral osteoarthritis: a pilot study

Increased joint stress and malalignment are etiologic factors in osteoarthritis. Static tibiofemoral frontal plane malalignment is associated with patellofemoral osteoarthritis (PFOA). Patellofemoral joint stress is increased by activities such as sit-to-stand (STS); this stress may be even greater if dynamic frontal plane tibiofemoral malalignment occurs. If hip muscle or quadriceps weakness is present in persons with PFOA, aberrant tibiofemoral frontal plane movement may occur, with increased patellofemoral stress. No studies have investigated frontal plane tibiofemoral and hip kinematics during STS in persons with PFOA or the relationship of hip muscle and quadriceps strength to these motions. Eight PFOA and seven control subjects performed STS from a stool during three-dimensional motion capture. Hip muscle and quadriceps strength were measured as peak isometric force. The PFOA group demonstrated increased peak tibial abduction angles during STS, and decreased hip abductor, hip extensor, and quadriceps peak force versus controls. A moderate inverse relationship between peak tibial abduction angle and peak hip abductor force was present. No difference between groups was found for peak hip adduction angle or peak hip external rotator force. Dynamic tibiofemoral malalignment and proximal lower extremity weakness may cause increased patellofemoral stress and may contribute to PFOA incidence or progression.

Gluteal muscle activation during the isometric phase of squatting exercises with and without a Swiss ball

OBJECTIVES

Growing evidence supports hip muscle activation and strengthening exercise prescription to prevent and treat various lower limb injuries. Common prescriptions include single-legged and double-legged squatting, with and without a Swiss ball. We aimed to establish the effect of varying forms of squatting exercises on gluteal muscle activation.

DESIGN AND SETTING

Observational laboratory study.

PARTICIPANTS

Nineteen (11 male) healthy participants (28.4 +/- 2.7 years old) were compared using one-way repeated measures analysis of variance.

MAIN OUTCOME MEASURES

Surface electromyography (EMG) measures of gluteus medius (GMed) and gluteus maximus (GMax) during the isometric phase of single-legged and double-legged squatting, with and without a Swiss ball.

RESULTS

A greater percentage of maximal voluntary contraction (%MVC) during single-legged squatting was found compared to double-legged squatting for GMed (42 versus 9%MVC, p < 0.001) and GMax (35 versus 14%MVC, p < 0.001). Additionally, the Swiss ball increased GMax activity (42 versus 35%MVC, p = 0.026) and demonstrated a trend toward increased GMed activity (46 versus 42%MVC, p = 0.075) during the single-legged squat.

CONCLUSIONS

These results indicate single-legged squatting may be more appropriate than double-legged squatting to facilitate strength gains of GMed and GMax. Additionally, the Swiss ball may be a useful adjunct to target gluteal muscle strengthening during single-legged squatting.

The influence of forefoot varus on eccentric hip torque in adolescents

Hip strength impairments have been established as risk factors for lower limb injuries. Hip muscles strength might be influenced by foot misalignments, however this has not yet been verified. Forefoot varus (FV) has been shown to cause subtalar joint hyperpronation. Subtalar hyperpronation has been associated with excessive lower limb internal rotation in weight-bearing activities. Also, subtalar hyperpronation might result in greater ground reaction force dissipation at the foot. Consequently, there would be less demand for force dissipation at the hip joint, which could reduce the capacity for hip eccentric torque in these subjects. Therefore, the purpose of this study was to determine if FV influences the eccentric hip torque generation of young subjects. Forty-four sedentary, healthy adolescents were divided into 2 groups: subjects with FV (VG, n = 22) and subjects with neutral forefoot alignment (CG, n = 22). An isokinetic dynamometer was used to assess the eccentric torque generated in hip extension and external rotation in these subjects. Group differences were assessed using a one-way multivariate analysis of variance. The VG presented smaller eccentric torque for hip extension (P = 0.014) when compared to the CG, with no difference between groups in external rotation torque (P = 0.433). These results indicate that FV influences hip eccentric torque generation of young subjects. Considering that the muscles involved in hip extension are related to the stabilization of the lumbar spine, hip and knee, these findings bring further enlightenment to the role of foot misalignments as risk factors for injuries in the lower limbs and lumbo-pelvic complex in young subjects.

Avaliação isocinética, dor e funcionalidade de sujeitos com síndrome da dor patelofemoral

Este estudo visou determinar a influência da Síndrome da Dor Patelofemoral (SDPF) sobre o pico de torque e trabalho da musculatura flexora e extensora do joelho, além de avaliar a dor e funcionalidade de sujeitos com a disfunção. Participaram 52 sujeitos do gênero feminino, 23 com SDPF e 29 clinicamente saudáveis similares em idade, estatura e massa corporal. A avaliação isocinética foi realizada no modo concêntrico para os flexores e extensores do joelho nas velocidades de 60 e 180°/s. Também foi aplicada a Escala Visual Numérica antes e após cada velocidade do teste isocinético e o questionário de Kujala. Os dados foram analisados pela estatística descritiva e inferencial (testes U de Mann-Whitney, Wilcoxon e t independente) com nível de significância de α=0,05. O Grupo com Síndrome da Dor Patelofemoral (GSDPF) apresentou menor pontuação (p=0,01) no questionário de Kujala (75,7±12,3 pontos) em relação ao Grupo Controle (GC) (100±0,0 pontos), além de menor pico de torque, tanto em 60 como 180°/s, dos flexores (0,82±0,24 Nm/kg; 0,51±0,22 Nm/kg) e extensores (1,85±0,48 Nm/kg; 1,13±0,44 Nm/kg) do joelho, bem como menor trabalho total dos extensores do joelho a 180°/s (6,46±2,54 J/kg) e 60°/s (9,42±3,27 J/kg). Além disso, foi observado aumento da dor do GSDPF após a avaliação isocinética a 180°/s (0,9 cm) e 60°/s (2,3 cm). Os resultados evidenciaram que sujeitos com SDPF possuem menor capacidade funcional e menor pico de torque e trabalho dos flexores e extensores do joelho, sugerindo que o fortalecimento desta musculatura deve ser considerado na reabilitação destes sujeitos.

Description of a weight-bearing method to assess hip abductor and external rotator muscle performance

STUDY DESIGN

Measurements, descriptive.

OBJECTIVES

To describe a weight-bearing method to assess bilateral hip abductor and external rotator muscle performance.

BACKGROUND

The hip abductors and external rotators are important in maintaining lower extremity alignment during weight-bearing tasks. As such, there is a need for a method to assess hip muscle performance in weight bearing.

METHODS

The weight-bearing method of assessing hip muscle performance utilized a force transducer connected to a nonstretchable fabric strap positioned around the distal ends of both thighs (proximal to the lateral epicondyles). The force generation capacity was recorded with the participants in a semi-squat position (30° of hip flexion and 50° of knee flexion). To establish the reliability of the measurement, 20 participants were tested on 2 separate days, and intraclass correlation coefficient (model 3,1) and standard error of measurement were calculated to evaluate test-retest reliability and intersession consistency. The level of agreement between the muscle performance values obtained using the weight-bearing method and the traditional non-weight-bearing method of testing hip abduction in sidelying (dynamometer) was assessed using a linear correlation model.

RESULTS

The weight-bearing method of assessing hip muscle performance was reliable (intraclass correlation coefficient = 0.99; 95% confidence interval: 0.97, 0.99) and consistent (standard error of measurement, 0.02 N/kg). The measured strength using the weight-bearing method was moderately associated with hip abduction strength values measured in non-weight bearing (r = 0.75, P<.01).

CONCLUSION

The proposed weight-bearing method of assessing hip abductor and external rotator muscle performance can be used as a simple, economic, and reliable method to assess hip muscle strength.

Outcomes of endoscopic gluteus medius repair with minimum 2-year follow-up

BACKGROUND

Gluteus medius tears may be present in as many as 25% of late middle-aged women and 10% of middle-aged men, and they are often misdiagnosed. Outcomes of endoscopic repair of gluteus medius tears have seldom been reported.

PURPOSE

To report the early outcomes of endoscopic repair of partial- and full-thickness gluteus medius tears.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between April 2009 and January 2010, data were prospectively collected for all patients undergoing endoscopic gluteus medius repair by one of the authors. Inclusion criteria for the study were patients undergoing repair for either high-grade, partial-, or full-thickness tears. Only patients with endoscopic evidence of a gluteus medius tear were treated surgically. In the case of an articular-side tear, a transtendinous repair technique was used, whereas in the presence of a full-thickness tear, the tendon was refixated to the bone directly.

RESULTS

A total of 15 patients met the inclusion criteria. The cohort included 14 women and 1 man, with an average age of 58 years (range, 44-74 years). Endoscopically, 6 cases were found to be partial-thickness tears. Nine were either full-thickness tears or near-full-thickness tears, which were completed for the repair. Follow-up was obtained on all patients at an average of 27.9 months postoperatively (range, 24-37 months). Fourteen of the 15 patients showed postoperative improvement in all 4 hip-specific scores used to assess outcome, with an average improvement of more than 30 points for all scores. Satisfaction with the surgery results was reported to be from good to excellent (scores of 7-10 out of 10) in 14 of 15 patients.

CONCLUSION

This study demonstrates that endoscopic surgical repair, whether performed through a transtendinous or full-thickness technique, can be an effective treatment of gluteus medius tears at a minimum follow-up of 2 years. Longer term follow-up studies are necessary to determine whether these therapeutic and functional gains are maintained.